1. Field of the Invention
The present invention relates to the synthesis of 1,2-dichloroethane by oxychlorination of ethylene by means of carbon tetrachloride.
2. Description of the Prior Art
It is known to this art that chlorination of ethylene produces 1,2-dichloroethane (D12) which, by simple pyrolysis, is converted into vinyl chloride (VCM) and hydrochloric acid (HCl). HCl is recycled to produce D12 according to the following oxychlorination reaction mechanism (1): EQU 2C.sub.2 H.sub.4 +O.sub.2 +4 HCl.fwdarw.2C.sub.2 H.sub.4 Cl.sub.2 +2 H.sub.2 O (1)
This oxychlorination reaction makes it possible to utilize the chlorine contained in the HCl.
The above processes are described in Ullmann's Encyclopedia Of Chemical Industry, 5th edition, volume A 6, pages 263-270 and 283-291.
French Patent No. 2,260,551 describes the oxychlorination of heavy chlorinated residues, namely, the reaction between these residues of ethylene and oxygen to produce perchloroethylene, trichloroethane, tetrachloroethane and D12.
South African Patent Application No. 71-5,781, published Mar. 27, 1972, describes a process for the oxychlorination of ethylene, to prepare a mixture of perchloroethylene and trichloroethylene.
According to this prior art, the ethylene, the oxygen and the chlorine are passed over a fluidized bed catalyst based on copper chloride deposited onto a porous support, at a temperature ranging from 410.degree. to 440.degree. C. The reaction is carried out in the presence of carbon tetrachloride originating from the recycling of the products exiting the fluidized bed. The products exiting the fluidized bed are cooled to condense perchloroethylene, trichloroethylene and carbon tetrachloride. The latter (CCl.sub.4) is mixed with the feed gases (C.sub.2 H.sub.4, Cl.sub.2 and air) and is thus recycled to the fluidized bed. The perchloroethylene and trichloroethylene constitute at least 50 mol % of the chlorinated products exiting the fluidized bed. The amount of CCl.sub.4 is constant and the CCl.sub.4 does not accumulate. Its concentration does not exceed 10 mol % relative to the organic compounds charged into the fluidized bed, and this corresponds to a few percent relative to the total amount of the inlet gases. The amount of chlorine, in the form of Cl.sub.2, ranges from 40% to 75% of the chlorine-containing reactants introduced into the fluidized bed, about 2% to 8% is in the form of HCl and the remainder is organic chlorine-containing compounds (including CCl.sub.4). The atomic ratio of oxygen to carbon at the inlet to the fluidized bed ranges from 0.85 to 2. The overall result of this reaction, accordingly, is to produce perchloroethylene and trichloroethylene while consuming ethylene, chlorine (Cl.sub.2) and oxygen.